1. Field of the Invention
The present invention relates to an operating apparatus such as a vehicle operating pedal apparatus, and in particular to improvements to a load sensor-equipped operating apparatus that includes a load sensor which electrically detects operating force.
2. Description of Related Art
A load sensor-equipped operating apparatus is known which includes (a) an operational member which is movably operated; (b) a reaction force member that receives the operating force of the operational member transmitted thereto, and on which a reaction force corresponding to the operating force is acted; (c) at least one pivotal connecting portion which is located between the operational member and the reaction force member, and connects a pair of the members pivotably relative to each other to transmit the operating force; and (d) a load sensor which electrically detects the operating force. Patent Document 1 discloses a vehicle brake pedal apparatus as one example of this type of load sensor-equipped operating apparatus. In this apparatus, a push rod (reaction force member) protrudes from a master cylinder, and is connected axially-movably relative to a connecting pin which protrudes from a side of an operational pedal. A sensor detects displacement of the push rod which is displaced against bias force of a spring relative to the connecting pin.
Patent Document 1: U.S. Pat. No. 5,563,355
However, in the apparatus disclosed in Patent Document 1, the push rod is required to have an elongated hole to allow it to move axially relative to the connecting pin. For this reason, normal push rods cannot be used as they are. In addition to this, since the push rod is pivoted relative to the connecting pin when the operational pedal is depressed, the spring biasing the push rod and the sensor detecting the displacement are also required to be pivotable relative to the connecting pin. As a result, firstly, the structure of the apparatus becomes complicated. Secondly, since the push rod, the spring and the sensor are located on the side of the operational pedal, they are required to have a rigid structure which ensures a stably operative state. In particular, this requirement is important for a brake pedal and the like. Consequently, this type of apparatus is large-size and becomes expensive as a whole.
In relation to this, although not publicly known, a technology has been conceived which provides compact arrangement of a load sensor or load detecting sensor at the connection point of a clevis pin as shown in FIG. 16. An operating pedal apparatus 200 for a vehicle service brake is shown in FIG. 16. FIG. 16(a) is a front view of the operating pedal apparatus 200, and FIG. 16(b) is an enlarged cross-sectional view taken along a line XVIA-XVIA in FIG. 16(a). A plate-like operational pedal 16 is attached to a pedal support 12 which is integrally secured to a vehicle, to be pivotable about an axis of a substantially horizontal supporting shaft 14. A depression portion (pad) 18 is located at the lower end of the operational pedal 16 which is depressed by a driver when the braking operation is required, and an operating rod 22 of a brake booster is connected to the middle part of the operational pedal 16 via a pivotal connecting portion 20.
The pivotal connecting portion 20 includes a U-shaped clevis 24 which is integrally secured to the ends of the operating rod 22 by a screw connecting or the like, and a clevis pin 26 which is located in the operational pedal 16 in parallel to the support shaft 14. The operating rod 22 and the operational pedal 16 are pivotably connected relative to each other about an axis of the clevis pin 26. Both end portions or opposite end portions of the clevis pin 26 protrude from both sides of the operational pedal 16, and are locked into the U-shaped clevis 24 by a snap ring, a retaining pin or the like so as not to drop off from the clevis 24.
An output in accordance with the operating force of the operational pedal 16 is transmitted to the operating rod 22 via the pivotal connecting portion 20. A reaction force corresponding to the output is applied to the operational pedal 16 by a brake booster. That is, this operating rod 22 corresponds to a reaction force member. In a by-wire type operating pedal apparatus in which a wheel brake is electrically controlled, a reaction force member which is acted upon by a given amount of reaction force by a reaction force mechanism or the like is connected to the pivotal connecting portion 20 instead of the operating rod 22.
A sensor attaching hole 202 with a diameter larger than the clevis pin 26 is located at the connecting position of the operational pedal 16 where the operational pedal 16 is connected to the clevis pin 26. A load sensor 30 is arranged in the annular space between the sensor attaching hole 202 and the clevis pin 26. The load sensor 30 includes a cylindrical deformable member 32 which detects the load applied in the radial direction thereof. The load sensor 30 additionally includes a cylindrical annular member 34 arranged on an outer periphery side of the deformable member 32, and a shaft-like member 36 arranged on an inner periphery side of the deformable member 32. The annular member 34, corresponds to a claimed main body member, is integrally assembled to the sensor attaching hole 202 at a constant orientation (phase) by press fitting, or by a bolt, a leaf spring or the like. One axial end of the deformable member 32 (the upper end in FIG. 16(b)) is integrally retained to the annular member 34 by welding or the like.
The other axial end of the deformable member 32 (the lower end in FIG. 16(b)) is integrally retained to the shaft-like member 36 by welding or the like. The clevis pin 26 is inserted into an insertion hole 38 which is arranged in the axial part of the shaft-like member 36. The clevis pin 26 is rotatable relative to both the insertion hole 38 and the clevis 24. The clevis pin 26 rotates relative to one of the insertion hole 38 and the clevis 24 that has lower friction when the operational pedal 16 is depressed. Note that a bearing or a bushing may be arranged between the clevis pin and the insertion hole or the clevis in order to reduce friction.
The annular member 34 and the shaft-like member 36 are thus connected by the deformable member 32. When substantially no load is applied from the outside in a radial direction, i.e., in a direction perpendicular to the axis, the members 32, 34 and 36 are retained substantially concentrically to the axis of the clevis pin 26. When a load is applied in a radial direction between the annular member 34 and the shaft-like member 36 by the reaction force of the operating rod 22 with depression of the operational pedal 16, the deformable member 32 is shear-deformed. As a result, the annular member 34 on the operational pedal 16 side displaces relative to the shaft-like member 36 in the direction to be closer to the operating rod 22 (leftward in FIG. 16). An annular space is provided between the annular member 34 and the shaft-like member 36 to allow both the relative radial displacement therebetween, and the shear deformation of the deformable member 32.
The deformable member 32 is made of a metal material such as a ferritic stainless steel alloy which can be elastically deformed by being applied a load in a radial direction, and is shear-deformed in accordance with the operating force with depression of the operational pedal 16. A strain detecting element such as a strain resistance element attached on the outer or inner peripheral surface of the deformable member 32 to detect the shear strain of the deformable member 32 is connected to a control circuit portion of the vehicle via a wire harness 56. Depressing operating force is detected based on the electrical signal which is outputted from the strain detecting element.
In the vehicle operating pedal apparatus 200, at the pivotal connecting portion 20 that transmits the operating force applied to the operational pedal 16 to the operating rod 22, the sensor attaching hole 202 is provided in the operational pedal 16 pivotably connected by the clevis pin 26 to the operating rod 22. Owing to the cylindrical load sensor 30 arranged in the annular space between the sensor attaching hole 202 and the clevis pin 26, rotational moment such as torsion is suppressed, so that the operating pedal apparatus 200 can be constructed simple and compact as a whole. In addition to this, for peripheral members such as the operating rod 22 and the clevis 24, similar members used in conventional pedal apparatuses can be used, which constructs the apparatus at low cost.
However, even in the vehicle operating pedal apparatus 200, when the operational pedal 16 is pivoted about the support shaft 14 by a depressing operation, the operating rod 22 and the operational pedal 16 are also pivoted about the axis of the clevis pin 26. For this reason, the acting position of the load which is applied to the deformable member 32, in other words, the relative displacing direction between the shaft-like member 36 and the annular member 34, varies. This variation may cause variation in the detection value. The size, arrangement and the like of the strain detecting element is set to allow detection of the deformation of the deformable member 32, irrespective of such variation in the deformation position of the deformable member 32. Nevertheless, the deformation position of the deformable member 32 continuously moves in the circumferential direction, and deformation mode thereof is complicated and is likely to vary. For this reason, depending on relative spatial relationships between the operating rod 22 or the operational pedal 16, ensuring high detection accuracy may be difficult.
The present invention has been made in consideration of the above situations, and its object is, in a load sensor-equipped operating apparatus including a load sensor provided in a pivotal connecting portion, to improve the detection accuracy of the load sensor. The load sensor electrically detects operating force based on relative displacement between a shaft-like member and a main body member (annular member 34 in FIG. 16) in a direction perpendicular to an axis of the shaft-like member.